Field
The present disclosure relates to an apparatus and method for displaying an image and an apparatus and method for emitting light.
Description of the Related Art
These days, liquid crystal display apparatuses which use liquid crystal elements as display elements are widely deployed. However, a self-emitting type display apparatus which uses light emitting elements as display elements is being developed. For example, an LED (Light-Emitting Diode) or an organic EL (Electro Luminescence) element is used as the light emitting element. In a self-emitting type display apparatus, light emitting elements other than display elements are not necessary. In a self-emitting type display apparatus, the thickness of the display apparatus can be reduced in comparison with a liquid crystal display apparatus because a backlight unit, which is used in liquid crystal display apparatus, is not necessary. A self-emitting type organic EL display apparatus which uses organic EL elements has advantages including wide viewing angle and high response speed, etc. Therefore, it is expected that an organic EL display apparatus will become the main flat-panel display apparatus of the next generation of professional displays. In a self-emitting type display apparatus which can display color images, a light emitting element group composed of three light emitting elements, each having a different emission color, is used for each pixel. For example, the three light emitting elements consist of a red (R) element which emits red light, a green (G) element which emits green light, and a blue (B) element which emits blue light. In a self-emitting type display apparatus which can display color images, the color of each pixel (emission color of each light emitting element group) is adjustable by adjusting the ratio of the emission brightness of the three light emitting elements.
In a self-emitting type display apparatus, it is known that the emission brightness of the display elements changes based on elapsed time. Temporal changes in emission brightness occur due to temporal changes such as changes in I (electric current)−V (voltage) characteristics of the display elements. The electric current value, which passes through a driving transistor mounted on a pixel circuit for driving a display element (light emitting element), changes because the I−V characteristics of the display element changes. Then, the electric current value which passes through the display element changes because the electric current value which passes through the driving transistor changes. Consequently, the emission brightness of the display element changes because the electric current value which passes through the display element changes.
Generally, the three light emitting elements of a light emitting element group have different degrees of temporal change of emission brightness. Thus, the emission color of each light emitting element group changes based on elapsed time because of temporal change s of the emission brightness of display elements.
FIG. 16 depicts an example of the temporal change of the emission brightness of a R element, a G element, and a B element, each of which is an organic EL element. As described in FIG. 16, the temporal change speed of the emission brightness of the B element is the fastest, and the temporal change speed of the emission brightness of the G element is the slowest. Thus, in association with increased driving time (energization time) of a light emitting element group, the ratio of the emission brightness of the R element, the G element and the B element changes based on elapsed time. For example, even if the ratio of the emission brightness of the R element, the G element, and the B element is 1:1:1 in an initial state, the ratio of the emission brightness changes to 0.9:1:0.6 based on elapsed time in association with an increased driving time of the light emitting element group. Then, the emission color of the light emitting element group changes based on elapsed time because the ratio of the emission brightness changes based on elapsed time. For example, the emission color of the light emitting element group shifts toward green in comparison with the emission color in the initial state, because the temporal change speed of the emission brightness of the G element is the slowest among the R element, the G element, and the B element.
The above-described temporal changes of the emission color occurs not only in self-emitting type display apparatus but also in light emitting apparatus such as a backlight of a liquid crystal display, street lamp, and room light, etc.
For example, a manufacture's instruction manual “CANON HD Video Camera XA20/XA25, p. 148, 150” discloses adjustment technology for the emission color of organic EL light emitting element groups each of which consists of a R element, a G element, and a B element. FIG. 17 depicts an example parameter adjustment image of the prior reference. As described in FIG. 17, the emission color of light emitting element groups is adjusted by a user operation on a graphic operation image. Specifically, the graphic operation image described in FIG. 17 includes a R-operation-bar operable by a user and a B-operation-bar operable by a user. The emission brightness of the R elements is adjusted corresponding to a user's operation of the R-operation-bar, and the emission brightness of the B elements is adjusted corresponding to a user's operation of the B-operation-bar, causing the emission color of light emitting element groups to be adjusted. Thus, temporal changes of the emission color can be suppressed by adjusting the emission color of the light emitting element groups.
However, it is difficult to realize the intended emission color because the emission brightness of R elements and the emission brightness of B elements are adjusted individually in the above described technology. Specifically, because thousands of combinations of emission brightness of R elements and B elements exists, it is difficult to find a best combination of emission brightnesses of the R elements and the B elements to realize an intended emission color. It is also very difficult for users who are not familiar with color adjustment to operate two operation-bars to realize an intended emission color.
The present invention provides technology that enables easy adjustment of the emission color of light emitting element groups to an intended emission color.